Figure 3. CHO Cells at Passage #20 stained for ß-gal Expression

On day 1, CHO-K1 cells were seeded in a 6-well plate and were transfected with 2 µg/well of pBICEP-CMV-1+lacZ. Cells were grown in DMEM media supplemented with 10% FBS, 4 mM L-glutamine and 1 mg/ml G-418. At day 72, passage number reached 20. Cells were then fixed with 0.5% gluteraldehyde and stained using 0.25 mg/ml 5-Bromo-4-chloro-3-indolyl-ß-D-galactopyranoside (X-gal).